<html><head><META http-equiv="Content-Type" content="text/html; charset=iso-8859-1"><title>Apache Tomcat 7 Configuration Reference (7.0.42) - The Loader Component</title><meta name="author" content="Craig R. McClanahan"><style type="text/css" media="print">
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  " border="0"></a></td><td><h1><font face="arial,helvetica,sanserif">Apache Tomcat 7</font></h1><font face="arial,helvetica,sanserif">Version 7.0.42, Jul 2 2013</font></td><td><!--APACHE LOGO--><a href="http://www.apache.org/"><img src="../images/asf-logo.gif" align="right" alt="Apache Logo" border="0"></a></td></tr></table><table border="0" width="100%" cellspacing="4"><!--HEADER SEPARATOR--><tr><td colspan="2"><hr noshade size="1"></td></tr><tr><!--LEFT SIDE NAVIGATION--><td width="20%" valign="top" nowrap class="noPrint"><p><strong>Links</strong></p><ul><li><a href="../index.html">Docs Home</a></li><li><a href="index.html">Config Ref. Home</a></li><li><a href="http://wiki.apache.org/tomcat/FAQ">FAQ</a></li><li><a href="#comments_section">User Comments</a></li></ul><p><strong>Top Level Elements</strong></p><ul><li><a href="server.html">Server</a></li><li><a href="service.html">Service</a></li></ul><p><strong>Executors</strong></p><ul><li><a href="executor.html">Executor</a></li></ul><p><strong>Connectors</strong></p><ul><li><a href="http.html">HTTP</a></li><li><a href="ajp.html">AJP</a></li></ul><p><strong>Containers</strong></p><ul><li><a href="context.html">Context</a></li><li><a href="engine.html">Engine</a></li><li><a href="host.html">Host</a></li><li><a href="cluster.html">Cluster</a></li></ul><p><strong>Nested Components</strong></p><ul><li><a href="globalresources.html">Global Resources</a></li><li><a href="jar-scanner.html">JarScanner</a></li><li><a href="listeners.html">Listeners</a></li><li><a href="loader.html">Loader</a></li><li><a href="manager.html">Manager</a></li><li><a href="realm.html">Realm</a></li><li><a href="resources.html">Resources</a></li><li><a href="valve.html">Valve</a></li></ul><p><strong>Cluster Elements</strong></p><ul><li><a href="cluster.html">Cluster</a></li><li><a href="cluster-manager.html">Manager</a></li><li><a href="cluster-channel.html">Channel</a></li><li><a href="cluster-membership.html">Channel/Membership</a></li><li><a href="cluster-sender.html">Channel/Sender</a></li><li><a href="cluster-receiver.html">Channel/Receiver</a></li><li><a href="cluster-interceptor.html">Channel/Interceptor</a></li><li><a href="cluster-valve.html">Valve</a></li><li><a href="cluster-deployer.html">Deployer</a></li><li><a href="cluster-listener.html">ClusterListener</a></li></ul><p><strong>Other</strong></p><ul><li><a href="filter.html">Filter</a></li><li><a href="systemprops.html">System properties</a></li></ul></td><!--RIGHT SIDE MAIN BODY--><td width="80%" valign="top" align="left" id="mainBody"><h1>The Loader Component</h1><table border="0" cellspacing="0" cellpadding="2"><tr><td bgcolor="#525D76"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Table of Contents"><!--()--></a><a name="Table_of_Contents"><strong>Table of Contents</strong></a></font></td></tr><tr><td><blockquote>
<ul><li><a href="#Introduction">Introduction</a></li><li><a href="#Attributes">Attributes</a><ol><li><a href="#Common_Attributes">Common Attributes</a></li><li><a href="#Standard_Implementation">Standard Implementation</a></li><li><a href="#VirtualWebappLoader_Implementation">VirtualWebappLoader Implementation</a></li></ol></li><li><a href="#Nested_Components">Nested Components</a></li><li><a href="#Special_Features">Special Features</a><ol><li><a href="#Logging">Logging</a></li></ol></li></ul>
</blockquote></td></tr></table><table border="0" cellspacing="0" cellpadding="2"><tr><td bgcolor="#525D76"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Introduction"><strong>Introduction</strong></a></font></td></tr><tr><td><blockquote>

  <p>The <strong>Loader</strong> element represents the <em>web
  application class loader</em> that will be used to load Java
  classes and resources for your web application.  Such
  a class loader must follow the requirements of the Servlet
  Specification, and load classes from the following locations:</p>
  <ul>
  <li>From the <code>/WEB-INF/classes</code> directory inside your
      web application.</li>
  <li>From JAR files in the <code>/WEB-INF/lib</code> directory
      inside your web application.</li>
  <li>From resources made available by Catalina to all web
      applications globally.</li>
  </ul>

  <p>A Loader element MAY be nested inside a <a href="context.html">Context</a>
  component.  If it is not included, a default Loader configuration will be
  created automatically, which is sufficient for most requirements.</p>

  <p>For a more in-depth description of the class loader hierarchy
  that is implemented by Catalina, see <a href="../class-loader-howto.html">the ClassLoader HowTo</a>.</p>

    <blockquote><em>
    <p>The description below uses the variable name $CATALINA_BASE to refer the
    base directory against which most relative paths are resolved. If you have
    not configured Tomcat for multiple instances by setting a CATALINA_BASE
    directory, then $CATALINA_BASE will be set to the value of $CATALINA_HOME,
    the directory into which you have installed Tomcat.</p>
    </em></blockquote>

</blockquote></td></tr></table><table border="0" cellspacing="0" cellpadding="2"><tr><td bgcolor="#525D76"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Attributes"><strong>Attributes</strong></a></font></td></tr><tr><td><blockquote>

  <table border="0" cellspacing="0" cellpadding="2"><tr><td bgcolor="#828DA6"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Common Attributes"><!--()--></a><a name="Common_Attributes"><strong>Common Attributes</strong></a></font></td></tr><tr><td><blockquote>

    <p>All implementations of <strong>Loader</strong>
    support the following attributes:</p>

    <table border="1" cellpadding="5"><tr><th width="15%" bgcolor="#023264"><font color="#ffffff">Attribute</font></th><th width="85%" bgcolor="#023264"><font color="#ffffff">Description</font></th></tr><tr><td align="left" valign="center"><code class="attributeName">className</code></td><td align="left" valign="center">
        <p>Java class name of the implementation to use.  This class must
        implement the <code>org.apache.catalina.Loader</code> interface.
        If not specified, the standard value (defined below) will be used.</p>
      </td></tr><tr><td align="left" valign="center"><code class="attributeName">delegate</code></td><td align="left" valign="center">
        <p>Set to <code>true</code> if you want the class loader to follow
        the standard Java2 delegation model, and attempt to load classes from
        parent class loaders <strong>before</strong> looking inside the web
        application.  Set to <code>false</code> (the default) to have the
        class loader look inside the web application first, before asking
        parent class loaders to find requested classes or resources.</p>
      </td></tr><tr><td align="left" valign="center"><code class="attributeName">reloadable</code></td><td align="left" valign="center">
        <p>Set to <code>true</code> if you want Catalina to monitor classes in
        <code>/WEB-INF/classes/</code> and <code>/WEB-INF/lib</code> for
        changes, and automatically reload the web application if a change
        is detected.  This feature is very useful during application
        development, but it requires significant runtime overhead and is
        not recommended for use on deployed production applications.  You
        can use the <a href="../manager-howto.html">Manager</a> web
        application, however, to trigger reloads of deployed applications
        on demand.</p>

        <p><strong>NOTE</strong> - The value for this property will be
        inherited from the <code>reloadable</code> attribute you set on
        the surrounding <a href="context.html">Context</a> component,
        and any value you explicitly set here will be replaced.</p>
      </td></tr></table>

  </blockquote></td></tr></table>


  <table border="0" cellspacing="0" cellpadding="2"><tr><td bgcolor="#828DA6"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Standard Implementation"><!--()--></a><a name="Standard_Implementation"><strong>Standard Implementation</strong></a></font></td></tr><tr><td><blockquote>

    <p>The standard implementation of <strong>Loader</strong> is
    <strong>org.apache.catalina.loader.WebappLoader</strong>.
    It supports the following additional attributes (in addition to the
    common attributes listed above):</p>

    <table border="1" cellpadding="5"><tr><th width="15%" bgcolor="#023264"><font color="#ffffff">Attribute</font></th><th width="85%" bgcolor="#023264"><font color="#ffffff">Description</font></th></tr><tr><td align="left" valign="center"><code class="attributeName">loaderClass</code></td><td align="left" valign="center">
        <p>Java class name of the <code>java.lang.ClassLoader</code>
        implementation class to use.  If not specified, the default value is
        <code>org.apache.catalina.loader.WebappClassLoader</code>. Custom
        <strong>loaderClass</strong> implementations must extend
        <code>org.apache.catalina.loader.WebappClassLoader</code>.</p>
      </td></tr><tr><td align="left" valign="center"><code class="attributeName">searchExternalFirst</code></td><td align="left" valign="center">
        <p>Set to <code>true</code> if you want repositories outside
        of <code>WEB-INF/classes</code> and <code>WEB-INF/lib</code> to
        be searched first. Default value is <code>false</code>.</p>
      </td></tr></table>

  </blockquote></td></tr></table>

  <table border="0" cellspacing="0" cellpadding="2"><tr><td bgcolor="#828DA6"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="VirtualWebappLoader Implementation"><!--()--></a><a name="VirtualWebappLoader_Implementation"><strong>VirtualWebappLoader Implementation</strong></a></font></td></tr><tr><td><blockquote>

    <p>This implementation of <strong>Loader</strong> is
    <strong>org.apache.catalina.loader.VirtualWebappLoader</strong>.
    It extends <code>WebappLoader</code> and supports the following
    additional attributes</p>

    <table border="1" cellpadding="5"><tr><th width="15%" bgcolor="#023264"><font color="#ffffff">Attribute</font></th><th width="85%" bgcolor="#023264"><font color="#ffffff">Description</font></th></tr><tr><td align="left" valign="center"><code class="attributeName">virtualClasspath</code></td><td align="left" valign="center">
        <p>Additional repositories to search for resources.
        Multiple values can be joined using <code>;</code>
        as a separator.</p>
        <p>Leading and trailing whitespaces in values are ignored.
        If a value does not point to an existing directory or
        <code>*.jar</code> file, it is silently skipped.
        Diagnostic messages can be seen if you enable debug logging for
        the VirtualWebappLoader class.
        </p>
        <p>Example: <code>virtualClasspath="${catalina.base}/myapp_config"</code></p>
      </td></tr><tr><td align="left" valign="center"><code class="attributeName">searchVirtualFirst</code></td><td align="left" valign="center">
        <p>Set to <code>true</code> if you want the virtual
        class path to be searched before
        <code>WEB-INF/classes</code> and <code>WEB-INF/lib</code>.
        Default value is <code>false</code>.</p>
        <p>If searched before, resources located in the virtual
        class path take precendence over resources with the same
        name contained in the webapp.</p>
      </td></tr></table>

  </blockquote></td></tr></table>


</blockquote></td></tr></table><table border="0" cellspacing="0" cellpadding="2"><tr><td bgcolor="#525D76"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Nested Components"><!--()--></a><a name="Nested_Components"><strong>Nested Components</strong></a></font></td></tr><tr><td><blockquote>

  <p>No components may be nested inside a <strong>Loader</strong> element.</p>

</blockquote></td></tr></table><table border="0" cellspacing="0" cellpadding="2"><tr><td bgcolor="#525D76"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Special Features"><!--()--></a><a name="Special_Features"><strong>Special Features</strong></a></font></td></tr><tr><td><blockquote>

  <table border="0" cellspacing="0" cellpadding="2"><tr><td bgcolor="#828DA6"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Logging"><strong>Logging</strong></a></font></td></tr><tr><td><blockquote>

    <p>A loader is associated with the log category based on its classname.</p>

  </blockquote></td></tr></table>

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